1. Field of the Invention
The present invention relates generally to the field of gene therapy. More particularly, the present invention relates to a novel gene therapy method of treating solid tumors, papillomas and warts using an adenoviral vector, a combination of adenoviral vectors, other viral vectors, and non-viral DNA transporter systems.
2. Description of the Related Art
Direct introduction of therapeutic genes into malignant cells in vivo can provide an effective treatment of localized tumors. Several novel treatment modalities have recently been attempted. For example, one treatment involves the delivery of normal tumor suppressor genes and/or inhibitors of activated oncogenes into tumor cells. A second treatment involves the enhancement of immunogeneity of tumor cells in vivo by the introduction of cytokine genes. A third treatment involves the introduction of genes that encode enzymes capable of conferring to the tumor cells sensitivity to chemotherapeutic agents. The herpes simplex virus-thymidine kinase (HSV-TK) gene can specifically convert a nucleoside analog (ganciclovir) into a toxic intermediate and cause death in dividing cells. It has recently been reported by Culver et al. (Science 256:1550-1552, 1992) that after delivery of the HSV-TK gene by retroviral transduction, subsequent ganciclovir treatment effectively caused brain tumor regression in laboratory animals. An attractive feature of this treatment modality for localized tumors is the so called "by-stander" effect. In the "by-stander" effect, the HSV-TK expressing tumor cells prevent the growth of adjacent non-transduced tumor cells in the presence of ganciclovir. Thus, not every tumor cell has to express HSV-TK for effective cancer treatment.
The HSV-TK retrovirus used by Culver et al., however, was limited by low viral titer. Thus, effective treatment of brain tumors necessitated the inoculation into animals of virus-producing cells rather than the viral isolate itself. Additionally, in previous experiments with synergeneic rats treated with a retrovirus and ganciclovir, the tumors were necrotic and were invaded by macrophages and lymphocytes. In Example 1, below, athymic mice were used and the tumor cells were destoyed without apparent involvement of the cellular immune response. The prior art remains deficient in the lack of an efficient gene therapy technique for the treatment of solid tumors.